Aquarium backing unit



FIG. 1 is a perspective view taken from the top, front and left side of an aquarium backing unit showing our new design;

FIG. 2 is a perspective view taken from the top, rear and left side thereof;

FIG. 3 is a right-side view thereof;

FIG. 4 is a bottom view thereof;

FIG. 5 is a cross-sectional view taken along line 5--5 of FIG. 1.

The broken line representation of an electric cord in FIG. 2 is for purposes of illustration only and forms no part of the claimed design. 

The ornamental design for an aquarium backing unit, as shown and described. 